security/tor-browser: Add U2F support to NetBSD.

The webauthn API is disabled by default in the Tor Browser:

https://gitlab.torproject.org/tpo/applications/tor-browser/-/issues/26614

In order to use it, risking the consequences since the Tor Project
has not audited its anonymity properties, you have to explicitly
enable security.webauthn.webauthn=true in about:config.

So if you definitely want to log into a web site using U2F in spite
of that, with location privacy but not anonymity, then these patches
now enable it to work on NetBSD (with the caveat that enabling
security.webauthn.webauthn=true applies also to any web site that
tries to use the webauthn API, not just the ones you want to log
into).

(riastradh)